A useful composite rope (as used herein, the term "rope" is used in a generic sense, and includes materials sometimes referred to by terms such as "wire" and "cable") of fibers, which has a high tensile strength and low elongation approximately equal to that of conventional wire rope, but which is ligher than conventional wire rope and shows little expansion and contraction upon the variation of temperature, is described in Japanese Patent Publication No. 57-25679, corresponding to U.S. Pat. No. 4,050,230.
In the manufacture of said composite rope, as shown in FIG. 1, a fiber core (a) is formed from several yarns (bundle of filaments which are twisted) or strands (bundle of filaments which are not twisted) of fiber having high tensile strength and low elongation, the fiber core (a) is introduced into a thermosetting resin containing bath (b) to impregnate the fiber core (a) with the thermosetting resin. The fiber core (a) is then led into a series of shaping dies (c) to provide a desired cross-sectional shape and to remove excess resin. Thereafter, the fiber core (a) is led into the cross head (e) of a melting extruder (d), in which the peripheral surface of said fiber core (a) is coated tightly with a thermoplastic resin such as polyethylene resin or the like, which is molten at about 130.degree. C., in a constant thickness of, in general, from about 0.5 to 1 mm. After coating, the fiber core (a) is run immediately into a cooling water bath (f) to cool and solidify the resin coat layer resulting in a composite rope (a.sub.1). The resulting composite rope (a.sub.1) may be used alone after the thermosetting resin in the rope is cured, or several of said composite ropes in which the thermosetting resin is uncured, that is to say, under such condition that the composite rope (a.sub.1) is still soft, are led into a braiding machine (g), as shown in FIG. 2, to braid the same, they are then led into a hot water bath (h) to completely cure the thermosetting resin in each composite rope (a.sub.1) and form a stable useful rope (a.sub.2).
In the above mentioned process, the fiber core (a) is led through the thermosetting resin bath (b) and the peripheral surface thereof is then coated with a thermoplastic resin (e.g., polyethylene), which is then cured, in order to prevent the leakage of uncured thermosetting resin from the fiber core. However, when the coated layer is thin, it may be easily broken, thus not achieving the intended purposes. Therefore, it is necessary to keep the thickness of said coated layer thicker than a certain value. However, the thicker the coated layer is, the higher is the weight and the section diameter of the composite rope (a.sub.1), so that the tensile strength per section diameter tends to be decreased. Further, the above mentioned coat of polyethylene and the like can not prevent at all degradation cuased by the mutual abrasion of yarns and strands due to excessive elongation of said coat. The tensile strength of the coat is low, so that it could not be expected to improve at all the bend strength thereof.